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  <th width=33% align=left>RINETD(8)
  <th width=33% align=right>Unix System Manager's Manual
  <th width=33% align=right>RINETD(8)
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<h3>NAME</h3>

<p> rinetd -- internet “redirection server”</p>

<h3>SYNOPSIS</h3>

<p> <code>/usr/sbin/rinetd</code></p>

<h3>VERSION</h3>

<p> Version 0.63, 2017/07/19. Version 0.63 corrects several bugs including a
denial of service security issue, and greatly improves performance, ease of
use, and portability. </p>

<h3>WHERE TO GET</h3>
 <p> <a href="https://github.com/samhocevar/rinetd/releases">By HTTP on
GitHub</a> in the releases section. </p>

<h3>DESCRIPTION</h3>

<p> Redirects TCP connections from one IP address and port to another. rinetd
is a single-process server which handles any number of connections to the
address/port pairs specified in the file <code>/etc/rinetd.conf</code>. Since
rinetd runs as a single process using nonblocking I/O, it is able to redirect
a large number of connections without a severe impact on the machine. This
makes it practical to run TCP services on machines inside an IP masquerading
firewall. rinetd <strong>does not redirect FTP</strong>, because FTP requires
more than one socket. </p>

<p> rinetd is typically launched at boot time, using the following syntax: </p>

<blockquote>/usr/sbin/rinetd</blockquote>

<p> The configuration file is found in the file <code>/etc/rinetd.conf</code>,
unless another file is specified using the <code>-c</code> command line option.
</p>

<h3>FORWARDING RULES</h3>

<p> Most entries in the configuration file are forwarding rules. The format of
a forwarding rule is as follows:
  <blockquote>bindaddress bindport connectaddress connectport</blockquote>
For example:
  <blockquote>206.125.69.81 80 10.1.1.2 80</blockquote>
Would redirect all connections to port 80 of the “real” IP address
206.125.69.81, which could be a virtual interface, through rinetd to port 80
of the address 10.1.1.2, which would typically be a machine on the inside of a
firewall which has no direct routing to the outside world. </p>

<p> Although responding on individual interfaces rather than on all interfaces
is one of rinetd's primary features, sometimes it is preferable to respond on
all IP addresses that belong to the server. In this situation, the special IP
address <code>0.0.0.0</code> can be used. For example:
  <blockquote>0.0.0.0 23 10.1.1.2 23</blockquote>
Would redirect all connections to port 23, for all IP addresses assigned to the
server. This is the default behavior for most other programs. </p>

<p> Service names can be specified instead of port numbers. On most systems,
service names are defined in the file /etc/services. </p>

<p> Both IP addresses and hostnames are accepted for bindaddress and
connectaddress. </p>

<h3>ALLOW AND DENY RULES</h3>

<p> Configuration files can also contain allow and deny rules. </p>

<p> Allow rules which appear before the first forwarding rule are applied
globally: if at least one global allow rule exists, and the address of a new
connection does not satisfy at least one of the global allow rules, that
connection is immediately rejected, regardless of any other rules. </p>

<p> Allow rules which appear after a specific forwarding rule apply to that
forwarding rule only. If at least one allow rule exists for a particular
forwarding rule, and the address of a new connection does not satisfy at least
one of the allow rules for that forwarding rule, that connection is immediately
rejected, regardless of any other rules. </p>

<p> Deny rules which appear before the first forwarding rule are applied
globally: if the address of a new connection satisfies any of the global deny
rules, that connection is immediately rejected, regardless of any other rules.
</p>

<p> Deny rules which appear after a specific forwarding rule apply to that
forwarding rule only. If the address of a new connection satisfies any of the
deny rules for that forwarding rule, that connection is immediately rejected,
regardless of any other rules. </p>

<p> The format of an allow rule is as follows:
  <blockquote>allow pattern</blockquote>
Patterns can contain the following characters: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, .
(period), ?, and *. The ? wildcard matches any one character. The * wildcard
matches any number of characters, including zero. </p>

<p> For example: </p>

<p> <blockquote>allow 206.125.69.*</blockquote>
This allow rule matches all IP addresses in the 206.125.69 class C domain. </p>

<p> Host names are NOT permitted in allow and deny rules. The performance cost
of looking up IP addresses to find their corresponding names is prohibitive.
Since rinetd is a single process server, all other connections would be forced
to pause during the address lookup. </p>

<h3>LOGGING</h3>

<p> rinetd is able to produce a log file in either of two formats:
tab-delimited and web server-style “common log format.” </p>

<p> By default, rinetd does not produce a log file. To activate logging, add
the following line to the configuration file:
  <blockquote>logfile log-file-location</blockquote>
Example:
  <blockquote>logfile /var/log/rinetd.log</blockquote>
By default, rinetd logs in a simple tab-delimited format containing the
following information: </p>

<ul>
 <li> Date and time </li>
 <li> Client address<br />
 <li> Listening host </li>
 <li> Listening port </li>
 <li> Forwarded-to host </li>
 <li> Forwarded-to port </li>
 <li> Bytes received from client </li>
 <li> Bytes sent to client </li>
 <li> Result message </li>
</ul>

<p> To activate web server-style “common log format” logging, add the following
line to the configuration file:
  <blockquote>logcommon</blockquote>
</p>

<h3>COMMAND LINE OPTIONS</h3>

<p> The -c command line option is used to specify an alternate configuration
file. </p>

<p> The -f command line option is used to run rinetd in the foreground, without
forking to the background. </p>

<p> The -h command line option produces a short help message. </p>

<p> The -v command line option displays the version number. </p>

<h3>REINITIALIZING RINETD</h3>

<p> The kill -1 signal (SIGHUP) can be used to cause rinetd to reload
its configuration file <strong>without</strong> interrupting existing
connections. Under Linux(tm) the process id is saved in the file
<code>/var/run/rinetd.pid</code> to facilitate the kill -HUP. An alternate file
name can be provided by using the <code>pidlogfile</code> configuration file
option. </p>

<h3>BUGS</h3>

<p> The server redirected to is not able to identify the host the client
really came from. This cannot be corrected; however, the log produced by
rinetd provides a way to obtain this information. Under Unix, sockets would
theoretically lose data when closed with <code>SO_LINGER</code> turned off, but
in Linux this is not the case (kernel source comments support this belief on
my part). On non-Linux Unix platforms, alternate code which uses a different
trick to work around blocking <code>close()</code> is provided, but this code
is untested. </p>

<p> The logging is inadequate. The duration of the connection should be logged.
</p>

<h3>LICENSE</h3>

<p> Copyright (c) 1997, 1998, 1999,
<a href="http://www.boutell.com/boutell">Thomas Boutell</a> and
<a href="http://www.boutell.com/">Boutell.Com, Inc.</a> </p>

<p> Copyright (c) 2003&mdash;2017 <a href="https://github.com/samhocevar">Sam
Hocevar</a> </p>

<p> This software is released for free use under the terms of the GNU
General Public License, version 2 or higher. </p>

<h3>CONTACT INFORMATION</h3>

<p> See <a href="https://github.com/samhocevar/rinetd/releases">the rinetd web
page</a> for the latest release. </p>

<p> Thomas Boutell can be reached by email: <a
href="mailto:boutell@boutell.com">boutell@boutell.com</a> </p>

<p> Sam Hocevar can be reached by email: <a
href="mailto:sam@hocevar.net">sam@hocevar.net</a> </p>

<h3>THANKS</h3>

<p> Thanks are due to Bill Davidsen, Libor Pechachek, Sascha Ziemann, Joel
S. Noble, the Apache Group, and many others who have contributed advice,
encouragement and/or source code to this and other open software projects. </p>

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